Field of the Invention
The present invention generally relates to oil seals of the type for sealing between rotatable members and particularly relates to oil seals provided with elastomeric ribs for preventing rotation of the seal about a shaft or within a bore.
In automobile and truck applications the wheel hubs are rotatably mounted on bearings supported on stationary axles. To keep these bearings lubricated at all times, an oil-filled space is generally provided adjacent the bearings. Oil seals are provided between the hub and the axle for preventing oil from leaking out of the bearings, keeping lubrication within the bearings and sealing the bearings from harmful contamination by outside dirt.
Prior oil seals have included a single-piece bore seal having a portion secured in sealing engagement in a bore in a hub, and a lip portion surrounding the axle for sealing during rotation between the hub and the axle. A problem associated with these seals is rapid lip wear caused by contact with axle surfaces not designed as sealing surfaces. To overcome this problem, some seals now include a rotational wear surface which is engaged by a sealing lip to increase the useable life of the seal.
An example of such a seal is disclosed in Corsi, et al, U.S. Pat. No. 3,561,770. This seal includes an integral unit which has two members rotatable with respect to one another. One of the members is secured to the axle and the other secured to the bore in the hub. The members are rotationally sealed together. One of the members has a wear sleeve and the other member includes a rotational seal with an annular lip for engaging the wear sleeve member.
This arrangement accommodates the rotational sealing engagement between the members since the outer member which is attached to the hub is rotatable with respect to the inner member which is attached to the axle. In such a seal the inner member includes a wear sleeve portion and the outer member has a rotational seal with a lip which is rotatable about and sealingly engages the wear sleeve surface. This allows for the use of a smooth wear sleeve surface which is designed for engagement by the lip of the seal in order to reduce seal wear.
While these seals have solved the problem of rapid seal wear, they require an oil impermeable seal not only between the two seal members but also at the place of seal engagement with the hub bore and around the periphery of the axle. These seals generally include a first annular surface which is press fit into the bore in a hub. The hub, along with the press fit seal, is then installed on the axle as a unit.
Elastomeric seals have been provided with radially extending annular ribs to stop rotational movement between an axle and the sealing member and to seal around the potentially rough surface of the axle. These ribs undergo relatively large radial deflections to produce the necessary frictional engagement with the axle to prevent rotation during use. This relatively high degree of rib deflection generates high levels of resistance to axial movement of the seal. This resistance must be overcome to install the seal onto and along the axle. Such a rib configuration is shown in Bradfute, et al, U.S. Pat. No. 3,356,376, which, while providing an advancement over the seals of the past has been somewhat cumbersome to install.
By compensating for slight imperfections in a bore or around an axle, and by facilitating installation, these types of seals have generally been considered an advancement over prior metal-to-metal contact seal designs. However, extreme care is necessary to ensure that the seal member is properly in position and is not excessively deformed during installation. Use of improper installation tools has frequently damaged and deformed these seals beyond design limits thereby reducing seal effectiveness.
Due to the necessary frictional engagement between the elastomeric seal and the axle's outer surface there must be a tight press fit between the seal and the axle necessitating high axial installation forces. These installation forces should be properly distributed around the periphery of the seal such that the seal may be evenly inserted on the axle to guard against excessive seal deformation. However, if uneven installation forces are applied to the seal, for instance by using improper tools, structural portions of the seal may be permanently deformed, causing the seal to malfunction.
Therefore, a need exists for an easily installed seal which reduces installation forces, minimizes the risk of damage during installation and which provides the necessary engagement with the axle or hub surface to prevent rotation therebetween.